Northern river otters are adapted to a variety of aquatic habitats from marine
environments to high-elevation mountain lakes. Optimum habitat for
northern river otters includes slow-moving water with deep pools, abundant
riparian vegetation, and plentiful fish . Northern river otters are generally
most abundant along food-rich coastal areas, such as the lower portions
of streams and rivers and in estuaries, and in areas having extensive
nonpolluted waterways . In Canada, they occur north beyond the tree
line in tundra lakes and streams .
Melquist and Hornocker  found that in west-central Idaho, river
otters prefer valley habitats to mountain habitats, and prefer
streamassociated habitats to lake, reservoir, and pond habitats.
Mountain lakes and streams were used most often during the fall. Most
northern river otters lived entirely in the valleys, and no otters lived solely
in the mountains. The use of lakes, reservoirs, and ponds was greatest
during the winter. Mudflats and associated open marshes, swamps, and
backwater sloughs were used most often in summer .
Northern river otter habitat is generally limited to open water during the
winter months. Outflows from lakes are favored habitat at this time.
In late winter, water levels usually drop below ice levels in rivers and
lakes, leaving a layer of air that allows northern river otters to travel and
hunt under the ice .
- 1. Banfield, A. W. F. 1974. The mammals of Canada. Toronto, ON: University of Toronto Press. 438 p. 
- 4. Chapman, Joseph A.; Feldhamer, George A., eds. 1982. Wild mammals of North America. Baltimore, MD: The Johns Hopkins University Press. 1147 p. 
- 6. Dronkert-Egnew, Ana E. 1991. River otter population status and habitat use in northwestern Montana. Missoula, MT: Univeristy of Montana. 112 p. Thesis. 
- 14. Melquist, Wayne E.; Hornocker, Maurice G. 1983. Ecology of river otters in west central Idaho. Wildlife Monographs. 83: 1-60. 
- 16. Spowart, Richard A.; Samson, Fred B. 1986. Carnivores. In: Cooperrider, Allan Y.; Boyd, Raymond J.; Stuart, Hanson R., eds. Inventory and monitoring of wildlife habitat. Denver, CO: U.S. Department of the Interior, Bureau of Land Management, Service Center: 475-496. 
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